// colddays.c -- 找出0℃以下的天数占总天数的百分比
#include<stdio.h>
int main(void)
{
    const int FREEZING = 0;     //0℃的定义
    float temperature;
    int cold_days = 0;
    int all_days = 0;

    printf("Enter the list of daily low temperatures.\n");
    printf("Use Celsius, and enter q to quit.\n");
    while (scanf("%f", &temperature) == 1)   //这里用scanf的返回值来判断循环是否进行
    {
        all_days++;      //执行循环则天数加1
        if(temperature < FREEZING)
          cold_days++;
    }
    if (all_days != 0)
       printf("%d days total: %.lf%% were below freezing.\n",    
               all_days, 100.0 * (float) cold_days / all_days);   //强制转化伟float类型
    if (all_days == 0)
       printf("No data entered!\n");

    return 0;    
}